96 OF STIMULUS AND EXERTION. SECT. XII. 5. 



are not much deranged by fmall variations of fti- 

 mulus ; as the quantity of fenforial power becomes 

 in fome meafure inversely as the quantity of fti- 

 mulus. 



3. A quantity of ftimulus lefs than that men- 

 tioned above, and, continued for fome time, in- 

 duces pain in the affected organ, as the pain of 

 cold in the hands, when they are immerfed in fnow, 

 is owing to a deficiency of the ftimulation of heat. 

 Hunger is a pain from the deficiency of the ftimula- 

 tion of food. Pain in the back at the commence- 

 ment of ague-fits, and the head-achs which attend 

 feeble people, are pains from defect of ftimulus, 

 and are hence relieved by opium, eflential oils, 

 fpirit of wine. 



As the pains, which originate from defect of 

 ftimulus, only occur in thofe parts of the fyftem, 

 which have been previoufly fubjected to perpetual 

 ftimulus ; and as an accumulation of fenforial power 

 is produced in the quiefcent organ along with the 

 pain, as in cold or hunger, there is reafon to 

 believe, that the pain is owing to the accumula- 

 tion of fenforial power, For, in the locomotive 

 mufcles, in the retina of the eye, and other organs 

 of fenfes, no pain occurs from the abfence of fti- 

 mulus, nor any great accumulation of fenforial 

 power beyond their natural quantity, fince thefe 

 organs have not been ufed to a perpetual fupply of 

 it. There is indeed a greater accumulation occurs 

 in the organ of vifion after its quiefcence, becaufe 

 it is fubject to more conftant ftimulus. 



4. A certain quantity of ftimulus lefs than natu- 

 ral induces the moving organ into feebler and 

 more frequent contractions, as mentioned in No. I. 

 4. of this Section. For each contraction moving 

 through a lefs fpace, or with lefs force, that is, 

 with lefs expenditure of the fpirit of animation, 

 is fooner relaxed, and the fpirit of animation 



derived 



